1 // Copyright 2017 The BoringSSL Authors
2 //
3 // Licensed under the Apache License, Version 2.0 (the "License");
4 // you may not use this file except in compliance with the License.
5 // You may obtain a copy of the License at
6 //
7 // https://www.apache.org/licenses/LICENSE-2.0
8 //
9 // Unless required by applicable law or agreed to in writing, software
10 // distributed under the License is distributed on an "AS IS" BASIS,
11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 // See the License for the specific language governing permissions and
13 // limitations under the License.
14
15 #include <openssl/bn.h>
16 #include <openssl/bytestring.h>
17 #include <openssl/span.h>
18
19 #define CHECK(expr) \
20 do { \
21 if (!(expr)) { \
22 printf("%s failed\n", #expr); \
23 abort(); \
24 } \
25 } while (false)
26
LLVMFuzzerTestOneInput(const uint8_t * buf,size_t len)27 extern "C" int LLVMFuzzerTestOneInput(const uint8_t *buf, size_t len) {
28 CBS cbs, child0, child1;
29 uint8_t sign0, sign1;
30 CBS_init(&cbs, buf, len);
31 if (!CBS_get_u16_length_prefixed(&cbs, &child0) ||
32 !CBS_get_u8(&child0, &sign0) ||
33 CBS_len(&child0) == 0 ||
34 !CBS_get_u16_length_prefixed(&cbs, &child1) ||
35 !CBS_get_u8(&child1, &sign1) ||
36 CBS_len(&child1) == 0) {
37 return 0;
38 }
39
40 bssl::UniquePtr<BIGNUM> numerator(
41 BN_bin2bn(CBS_data(&child0), CBS_len(&child0), nullptr));
42 BN_set_negative(numerator.get(), sign0 % 2);
43 bssl::UniquePtr<BIGNUM> divisor(
44 BN_bin2bn(CBS_data(&child1), CBS_len(&child1), nullptr));
45 BN_set_negative(divisor.get(), sign1 % 2);
46
47 if (BN_is_zero(divisor.get())) {
48 return 0;
49 }
50
51 bssl::UniquePtr<BN_CTX> ctx(BN_CTX_new());
52 bssl::UniquePtr<BIGNUM> result(BN_new());
53 bssl::UniquePtr<BIGNUM> remainder(BN_new());
54 CHECK(ctx);
55 CHECK(result);
56 CHECK(remainder);
57
58
59 CHECK(BN_div(result.get(), remainder.get(), numerator.get(), divisor.get(),
60 ctx.get()));
61 CHECK(BN_ucmp(remainder.get(), divisor.get()) < 0);
62
63 // Check that result*divisor+remainder = numerator.
64 CHECK(BN_mul(result.get(), result.get(), divisor.get(), ctx.get()));
65 CHECK(BN_add(result.get(), result.get(), remainder.get()));
66 CHECK(BN_cmp(result.get(), numerator.get()) == 0);
67
68 return 0;
69 }
70